Plasma processing apparatus

ABSTRACT

A plasma processing apparatus includes a balun having a first unbalanced terminal, a second unbalanced terminal, a first balanced terminal, and a second balanced terminal, a grounded vacuum container, a first electrode electrically connected to the first balanced terminal, a second electrode electrically connected to the second balanced terminal, and a ground electrode arranged in the vacuum container and grounded.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of International Patent ApplicationNo. PCT/JP2018/024154 filed on Jun. 26, 2018, which claims priority toand the benefit of International Patent Application No.PCT/JP2017/023611 filed Jun. 27, 2017, International Patent ApplicationNo. PCT/JP2017/023603 filed Jun. 27, 2017, and Japanese PatentApplication No. 2018-017548 filed Feb. 2, 2018, the entire disclosuresof which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a plasma processing apparatus.

BACKGROUND ART

There is provided a plasma processing apparatus that generates plasma byapplying a high frequency between two electrodes and processes asubstrate by the plasma. Such plasma processing apparatus can operate asan etching apparatus or a sputtering apparatus by the bias and/or thearea ratio of the two electrodes. The plasma processing apparatusconfigured as a sputtering apparatus includes the first electrode thatholds a target and the second electrode that holds a substrate. A highfrequency is applied between the first and second electrodes, and plasmais generated between the first and second electrodes (between the targetand the substrate). When plasma is generated, a self-bias voltage isgenerated on the surface of the target. This causes ions to collideagainst the target, and the particles of a material constituting thetarget are discharged from the target.

PTL 1 describes a sputtering apparatus including a grounded chamber, atarget electrode connected to an RF source via impedance matchingcircuitry, and a substrate holding electrode grounded via a substrateelectrode tuning circuit.

In the sputtering apparatus described in PTL 1, the chamber can functionas an anode in addition to the substrate holding electrode. Theself-bias voltage can depend on the state of a portion that can functionas a cathode and the state of a portion that can function as an anode.Therefore, if the chamber functions as an anode in addition to thesubstrate holding electrode, the self-bias voltage can change dependingon the state of a portion of the chamber that functions as an anode. Thechange in self-bias voltage changes a plasma potential, and the changein plasma potential can influence the characteristic of a film to beformed.

If a film is formed on a substrate using the sputtering apparatus, afilm can also be formed on the inner surface of the chamber. This maychange the state of the portion of the chamber that can function as ananode. Therefore, if the sputtering apparatus is continuously used, theself-bias voltage changes depending on the film formed on the innersurface of the chamber, and the plasma potential can also change.Consequently, if the sputtering apparatus is used for a long period, itis conventionally difficult to keep the characteristic of the filmformed on the substrate constant.

Similarly, if the etching apparatus is used for a long period, theself-bias voltage changes depending on the film formed on the innersurface of the chamber, and this may change the plasma potential.Consequently, it is difficult to keep the etching characteristic of thesubstrate constant.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Publication No. 55-35465

SUMMARY OF INVENTION Technical Problem

The present invention has been made based on the above problemrecognition, and provides a technique advantageous in stabilizing aplasma potential in long-term use.

According to one aspect of the present invention, there is provided aplasma processing apparatus comprising a balun including a firstunbalanced terminal, a second unbalanced terminal, a first balancedterminal, and a second balanced terminal, a grounded vacuum container, afirst electrode electrically connected to the first balanced terminal, asecond electrode electrically connected to the second balanced terminal,and a ground electrode arranged in the vacuum container and grounded.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the first embodiment of thepresent invention;

FIG. 2A is a circuit diagram showing an example of the arrangement of abalun;

FIG. 2B is a circuit diagram showing another example of the arrangementof the balun;

FIG. 3 is a circuit diagram for explaining the function of a balun 103;

FIG. 4 is a table exemplifying the relationship among currents I1 (=I2),I2′, and I3, ISO, and α (=X/Rp);

FIG. 5A is a timing chart showing a result of simulating a plasmapotential and a cathode potential when 1.5≤X/Rp≤5000 is satisfied;

FIG. 5B is a timing chart showing a result of simulating a plasmapotential and a cathode potential when 1.5≤X/Rp≤5000 is satisfied;

FIG. 5C is a timing chart showing a result of simulating a plasmapotential and a cathode potential when 1.5≤X/Rp≤5000 is satisfied;

FIG. 5D is a timing chart showing a result of simulating a plasmapotential and a cathode potential when 1.5≤X/Rp≤5000 is satisfied;

FIG. 6A is a timing chart showing a result of simulating a plasmapotential and a cathode potential when 1.5≤X/Rp≤5000 is not satisfied;

FIG. 6B is a timing chart showing a result of simulating a plasmapotential and a cathode potential when 1.5≤X/Rp≤5000 is not satisfied;

FIG. 6C is a timing chart showing a result of simulating a plasmapotential and a cathode potential when 1.5≤X/Rp≤5000 is not satisfied;

FIG. 6D is a timing chart showing a result of simulating a plasmapotential and a cathode potential when 1.5≤X/Rp≤5000 is not satisfied;

FIG. 7 is a circuit diagram exemplifying a method of confirming Rp−jXp;

FIG. 8 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the second embodiment of thepresent invention;

FIG. 9 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the third embodiment of thepresent invention;

FIG. 10 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the fourth embodiment of thepresent invention;

FIG. 11 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the fifth embodiment of thepresent invention;

FIG. 12 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the sixth embodiment of thepresent invention;

FIG. 13 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the seventh embodiment of thepresent invention;

FIG. 14 is a circuit diagram for explaining the function of a balunaccording to the sixth embodiment of the present invention;

FIG. 15A is a timing chart showing a result of simulating a plasmapotential and two cathode potentials when 1.5≤X/Rp≤5000 is satisfied;

FIG. 15B is a timing chart showing a result of simulating a plasmapotential and two cathode potentials when 1.5≤X/Rp≤5000 is satisfied;

FIG. 15C is a timing chart showing a result of simulating a plasmapotential and two cathode potentials when 1.5≤X/Rp≤5000 is satisfied;

FIG. 15D is a timing chart showing a result of simulating a plasmapotential and two cathode potentials when 1.5≤X/Rp≤5000 is satisfied;

FIG. 16A is a timing chart showing a result of simulating a plasmapotential and two cathode potentials when 1.5≤X/Rp≤5000 is notsatisfied;

FIG. 16B is a timing chart showing a result of simulating a plasmapotential and two cathode potentials when 1.5≤X/Rp≤5000 is notsatisfied;

FIG. 16C is a timing chart showing a result of simulating a plasmapotential and two cathode potentials when 1.5≤X/Rp≤5000 is notsatisfied;

FIG. 16D is a timing chart showing a result of simulating a plasmapotential and two cathode potentials when 1.5≤X/Rp≤5000 axis notsatisfied; and

FIG. 17 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the eighth embodiment of thepresent invention;

FIG. 18 is a circuit diagram showing the arrangement of a plasmaprocessing apparatus according to a comparative example;

FIG. 19 is a timing chart showing a simulation result of the operationof the plasma processing apparatus according to the comparative exampleshown in FIG. 18 ;

FIG. 20 is a timing chart showing a simulation result of the operationof the plasma processing apparatus according to the comparative exampleshown in FIG. 18 ;

FIG. 21 is a timing chart showing a simulation result of the operationof the plasma processing apparatus according to the comparative exampleshown in FIG. 18 ; and

FIG. 22 is a circuit diagram schematically showing the arrangement of aplasma processing apparatus 1 according to the ninth embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

The present invention will be described below with reference to theaccompanying drawings by way of exemplary embodiments.

FIG. 1 schematically shows the arrangement of a plasma processingapparatus 1 according to the first embodiment of the present invention.The plasma processing apparatus according to the first embodiment canoperate as a sputtering apparatus that forms a film on a substrate 112by sputtering. The plasma processing apparatus 1 includes a balun(balanced/unbalanced conversion circuit) 103, a vacuum container 110, afirst electrode 106, and a second electrode 111. Alternatively, it maybe understood that the plasma processing apparatus 1 includes the balun103 and a main body 10, and the main body 10 includes the vacuumcontainer 110, the first electrode 106, and the second electrode 111.The main body 10 includes a first terminal 251 and a second terminal252. The first electrode 106 may be arranged to separate a vacuum spaceand an external space (that is, to form part of a vacuum partition) incooperation with the vacuum container 110, or may be arranged in thevacuum container 110. The second electrode 111 may be arranged toseparate a vacuum space and an external space (that is, to form part ofa vacuum partition) in cooperation with the vacuum container 110, or maybe arranged in the vacuum container 110.

The balun 103 includes a first unbalanced terminal 201, a secondunbalanced terminal 202, a first balanced terminal 211, and a secondbalanced terminal 212. An unbalanced circuit is connected to the firstunbalanced terminal 201 and the second unbalanced terminal 202 of thebalun 103, and a balanced circuit is connected to the first balancedterminal 211 and the second balanced terminal 212 of the balun 103. Thevacuum container 110 is formed by a conductor, and is grounded.

In the first embodiment, the first electrode 106 serves as a cathode,and holds a target 109. The target 109 can be, for example, an insulatormaterial or a conductor material. Furthermore, in the first embodiment,the second electrode 111 serves as an anode, and holds the substrate112. The plasma processing apparatus 1 according to the first embodimentcan operate as a sputtering apparatus that forms a film on the substrate112 by sputtering the target 109. The first electrode 106 iselectrically connected to the first balanced terminal 211, and thesecond electrode 111 is electrically connected to the second balancedterminal 212. When the first electrode 106 and the first balancedterminal 211 are electrically connected to each other, this indicatesthat a current path is formed between the first electrode 106 and thefirst balanced terminal 211 so that a current flows between the firstelectrode 106 and the first balanced terminal 211. Similarly, in thisspecification, when a and b are electrically connected, this indicatesthat a current path is formed between a and b so that a current flowsbetween a and b.

The above arrangement can be understood as an arrangement in which thefirst electrode 106 is electrically connected to the first terminal 251,the second electrode 111 is electrically connected to the secondterminal 252, the first terminal 251 is electrically connected to thefirst balanced terminal 211, and the second terminal 252 is electricallyconnected to the second balanced terminal 212.

In the first embodiment, the first electrode 106 and the first balancedterminal 211 (first terminal 251) are electrically connected via ablocking capacitor 104. The blocking capacitor 104 blocks a DC currentbetween the first balanced terminal 211 and the first electrode 106 (orbetween the first balanced terminal 211 and the second balanced terminal212). Instead of providing the blocking capacitor 104, an impedancematching circuit 102 (to be described later) may be configured to blocka DC current flowing between the first unbalanced terminal 201 and thesecond unbalanced terminal 202. The first electrode 106 can be supportedby the vacuum container 110 via an insulator 107. The second electrode111 can be supported by the vacuum container 110 via an insulator 108.Alternatively, the insulator 108 can be arranged between the secondelectrode 111 and the vacuum container 110.

The plasma processing apparatus 1 can further include a high-frequencypower supply 101, and the impedance matching circuit 102 arrangedbetween the high-frequency power supply 101 and the balun 103. Thehigh-frequency power supply 101 supplies a high frequency(high-frequency current, high-frequency voltage, and high-frequencypower) between the first unbalanced terminal 201 and the secondunbalanced terminal 202 of the balun 103 via the impedance matchingcircuit 102. In other words, the high-frequency power supply 101supplies a high frequency (high-frequency current, high-frequencyvoltage, and high-frequency power) between the first electrode 106 andthe second electrode 111 via the impedance matching circuit 102, thebalun 103, and the blocking capacitor 104. Alternatively, thehigh-frequency power supply 101 can be understood to supply a highfrequency between the first terminal 251 and the second terminal 252 ofthe main body 10 via the impedance matching circuit 102 and the balun103.

A gas (for example, Ar, Kr, or Xe gas) is supplied to the internal spaceof the vacuum container 110 through a gas supply unit (not shown)provided in the vacuum container 110. In addition, the high-frequencypower supply 101 supplies a high frequency between the first electrode106 and the second electrode 111 via the impedance matching circuit 102,the balun 103, and the blocking capacitor 104. This generates plasmabetween the first electrode 106 and the second electrode 111, andgenerates a self-bias voltage on the surface of the target 109 to causeions in the plasma to collide against the surface of the target 109,thereby discharging, from the target 109, the particles of a materialconstituting the target 109. Then, the particles form a film on thesubstrate 112.

FIG. 2A shows an example of the arrangement of the balun 103. The balun103 shown in FIG. 2A includes a first coil 221 that connects the firstunbalanced terminal 201 and the first balanced terminal 211, and asecond coil 222 that connects the second unbalanced terminal 202 and thesecond balanced terminal 212. The first coil 221 and the second coil 222are coils having the same number of turns, and share an iron core.

FIG. 2B shows another example of the arrangement of the balun 103. Thebalun 103 shown in FIG. 2B includes a first coil 221 that connects thefirst unbalanced terminal 201 and the first balanced terminal 211, and asecond coil 222 that connects the second unbalanced terminal 202 and thesecond balanced terminal 212. The first coil 221 and the second coil 222are coils having the same number of turns, and share an iron core. Thebalun 103 shown in FIG. 2B further includes a third coil 223 and afourth coil 224 both of which are connected between the first balancedterminal 211 and the second balanced terminal 212. The third coil 223and the fourth coil 224 are configured so that the voltage of aconnection node 213 of the third coil 223 and the fourth coil 224 is setas the midpoint between the voltage of the first balanced terminal 211and that of the second balanced terminal 212. The third coil 223 and thefourth coil 224 are coils having the same number of turns, and share aniron core. The connection node 213 may be grounded, may be connected tothe vacuum container 110, or may be floated.

The function of the balun 103 will be described with reference to FIG. 3. Let I1 be a current flowing through the first unbalanced terminal 201,I2 be a current flowing through the first balanced terminal 211, I2′ bea current flowing through the second unbalanced terminal 202, and I3 bea current, of the current I2, flowing to ground. When I3=0, that is, nocurrent flows to ground on the balanced circuit side, the isolationperformance of the balanced circuit with respect to ground is highest.When I3=I2, that is, all the current I2 flowing through the firstbalanced terminal 211 flows to ground, the isolation performance of thebalanced circuit with respect to ground is lowest. An index ISOrepresenting the degree of the isolation performance is given by anequation below. Under this definition, as the absolute value of theindex ISO is larger, the isolation performance is higher.ISO [dB]=20 log(I3/I2′)

In FIG. 3 , Rp−jXp represents an impedance (including the reactance ofthe blocking capacitor 104) when viewing the side of the first electrode106 and the second electrode 111 (the side of the main body 10) from theside of the first balanced terminal 211 and the second balanced terminal212 in a state in which plasma is generated in the internal space of thevacuum container 110. Rp represents a resistance component, and −Xprepresents a reactance component. Furthermore, in FIG. 3 , X representsthe reactance component (inductance component) of the impedance of thefirst coil 221 of the balun 103. ISO has a correlation with X/Rp.

FIG. 4 exemplifies the relationship among the currents I1 (=I2), I2′,and I3, ISO, and α (=X/Rp). The present inventor found that thearrangement for supplying a high frequency between the first electrode106 and the second electrode 111 from the first high-frequency powersupply 101 via the balun 103, especially satisfying 1.5≤X/Rp≤5000 inthis arrangement is advantageous in making the potential (plasmapotential) of plasma formed in the internal space (the space between thefirst electrode 106 and the second electrode 111) of the vacuumcontainer 110 insensitive to the state of the inner surface of thevacuum container 110. When the plasma potential is insensitive to thestate of the inner surface of the vacuum container 110, this indicatesthat it is possible to stabilize the plasma potential even if the plasmaprocessing apparatus 1 is used for a long period. 1.5≤X/Rp≤5000corresponds to −10.0 dB≥ISO≥−80 dB.

FIGS. 5A to 5D each show a result of simulating the plasma potential andthe potential (cathode potential) of the first electrode 106 when1.5≤X/Rp≤5000 is satisfied. FIG. 5A shows the plasma potential and thecathode potential in a state in which no film is formed on the innersurface of the vacuum container 110. FIG. 5B shows the plasma potentialand the cathode potential in a state in which a resistive film (1,000 Ω)is formed on the inner surface of the vacuum container 110. FIG. 5Cshows the plasma potential and the cathode potential in a state in whichan inductive film (0.6 μH) is formed on the inner surface of the vacuumcontainer 110. FIG. 5D shows the plasma potential and the cathodepotential in a state in which a capacitive film (0.1 nF) is formed onthe inner surface of the vacuum container 110. With reference to FIGS.5A to 5D, it is understood that satisfying 1.5≤X/Rp≤5000 is advantageousin stabilizing the plasma potential in various states of the innersurface of the vacuum container 110.

FIGS. 6A to 6D each show a result of simulating the plasma potential andthe potential (cathode potential) of the first electrode 106 when1.5≤X/Rp≤5000 is not satisfied. FIG. 6A shows the plasma potential andthe cathode potential in a state in which no film is formed on the innersurface of the vacuum container 110. FIG. 6B shows the plasma potentialand the cathode potential in a state in which a resistive film (1,000 Ω)is formed on the inner surface of the vacuum container 110. FIG. 6Cshows the plasma potential and the cathode potential in a state in whichan inductive film (0.6 μH) is formed on the inner surface of the vacuumcontainer 110. FIG. 6D shows the plasma potential and the cathodepotential in a state in which a capacitive film (0.1 nF) is formed onthe inner surface of the vacuum container 110. With reference to FIGS.6A to 6D, it is understood that when 1.5≤X/Rp≤5000 is not satisfied, theplasma potential can change depending on the state of the inner surfaceof the vacuum container 110.

In both the case in which X/Rp>5000 (for example, X/Rp=∞) is satisfiedand the case in which X/Rp<1.5 (for example, X/Rp=1.0 or X/Rp=0.5) issatisfied, the plasma potential readily changes depending on the stateof the inner surface of the vacuum container 110. If X/Rp>5000 issatisfied, in a state in which no film is formed on the inner surface ofthe vacuum container 110, discharge occurs only between the firstelectrode 106 and the second electrode 111. However, if X/Rp>5000 issatisfied, when a film starts to be formed on the inner surface of thevacuum container 110, the plasma potential sensitively reacts to this,and the results exemplified in FIGS. 6A to 6D are obtained. On the otherhand, when X/Rp<1.5 is satisfied, a current flowing to ground via thevacuum container 110 is large. Therefore, the influence of the state ofthe inner surface of the vacuum container 110 (the electricalcharacteristic of a film formed on the inner surface) is conspicuous,and the plasma potential changes depending on formation of a film. Thus,as described above, the plasma processing apparatus 1 is advantageouslyconfigured to satisfy 1.5≤X/Rp≤5000.

A method of deciding Rp−jXp (it is desired to actually know only Rp)will be exemplified with reference to FIG. 7 . The balun 103 is detachedfrom the plasma processing apparatus 1 and an output terminal 230 of theimpedance matching circuit 102 is connected to the first terminal 251(blocking capacitor 104) of the main body 10. Furthermore, the secondterminal 252 (second electrode 111) of the main body 10 is grounded. Inthis state, the high-frequency power supply 101 supplies a highfrequency to the first terminal 251 of the main body 10 via theimpedance matching circuit 102. In the example shown in FIG. 7 , theimpedance matching circuit 102 is equivalently formed by coils L1 and L2and variable capacitors VC1 and VC2. It is possible to generate plasmaby adjusting the capacitance values of the variable capacitors VC1 andVC2. In the state in which the plasma is stable, the impedance of theimpedance matching circuit 102 matches the impedance Rp−jXp on the sideof the main body 10 (the side of the first electrode 106 and the secondelectrode 111) when the plasma is generated. The impedance of theimpedance matching circuit 102 at this time is given by Rp+jXp.

Therefore, Rp−jXp (it is desired to actually know only Rp) can beobtained based on the impedance Rp+jXp of the impedance matching circuit102 when the impedance is matched. Alternatively, for example, Rp−jXpcan be obtained by simulation based on design data.

Based on Rp obtained in this way, X/Rp can be specified. For example,the reactance component (inductance component) X of the impedance of thefirst coil 221 of the balun 103 can be decided based on Rp so as tosatisfy 1.5≤X/Rp≤5000.

FIG. 8 schematically shows the arrangement of a plasma processingapparatus 1 according to the second embodiment of the present invention.The plasma processing apparatus 1 according to the second embodiment canoperate as an etching apparatus that etches a substrate 112. In thesecond embodiment, a first electrode 106 serves as a cathode, and holdsthe substrate 112. In the second embodiment, a second electrode 111serves as an anode. In the plasma processing apparatus 1 according tothe second embodiment, the first electrode 106 and a first balancedterminal 211 are electrically connected via a blocking capacitor 104. Inother words, in the plasma processing apparatus 1 according to thesecond embodiment, the blocking capacitor 104 is arranged in anelectrical connection path between the first electrode 106 and the firstbalanced terminal 211.

FIG. 9 schematically shows the arrangement of a plasma processingapparatus 1 according to the third embodiment of the present invention.The plasma processing apparatus 1 according to the third embodiment is amodification of the plasma processing apparatus 1 according to the firstembodiment, and further includes at least one of a mechanism forvertically moving a second electrode 111 and a mechanism for rotatingthe second electrode 111. In the example shown in FIG. 9 , the plasmaprocessing apparatus 1 includes a driving mechanism 114 having both themechanism for vertically moving the second electrode 111 and themechanism for rotating the second electrode 111. A bellows 113 forming avacuum partition can be provided between a vacuum container 110 and thedriving mechanism 114.

Similarly, the plasma processing apparatus 1 according to the secondembodiment can further include at least one of a mechanism forvertically moving the first electrode 106 and a mechanism for rotatingthe first electrode 106.

FIG. 10 schematically shows the arrangement of a plasma processingapparatus 1 according to the fourth embodiment of the present invention.The plasma processing apparatus according to the fourth embodiment canoperate as a sputtering apparatus that forms a film on a substrate 112by sputtering. Items which are not referred to as the plasma processingapparatus 1 according to the fourth embodiment can comply with the firstto third embodiments. The plasma processing apparatus 1 includes a firstbalun 103, a second balun 303, a vacuum container 110, a first electrode106 and a second electrode 135 constituting the first pair, and a firstelectrode 141 and a second electrode 145 constituting the second pair.Alternatively, it may be understood that the plasma processing apparatus1 includes the first balun 103, the second balun 303, and a main body10, and the main body 10 includes the vacuum container 110, the firstelectrode 106 and the second electrode 135 constituting the first pair,and the first electrode 141 and the second electrode 145 constitutingthe second pair. The main body 10 includes a first terminal 251, asecond terminal 252, a third terminal 451, and a fourth terminal 452.

The first balun 103 includes a first unbalanced terminal 201, a secondunbalanced terminal 202, a first balanced terminal 211, and a secondbalanced terminal 212. An unbalanced circuit is connected to the firstunbalanced terminal 201 and the second unbalanced terminal 202 of thefirst balun 103, and a balanced circuit is connected to the firstbalanced terminal 211 and the second balanced terminal 212 of the firstbalun 103. The second balun 303 can have an arrangement similar to thatof the first balun 103. The second balun 303 includes a first unbalancedterminal 401, a second unbalanced terminal 402, a first balancedterminal 411, and a second balanced terminal 412. An unbalanced circuitis connected to the first unbalanced terminal 401 and the secondunbalanced terminal 402 of the second balun 303, and a balanced circuitis connected to the first balanced terminal 411 and the second balancedterminal 412 of the second balun 303. The vacuum container 110 isgrounded.

The first electrode 106 of the first pair holds a target 109. The target109 can be, for example, an insulator material or a conductor material.The second electrode 135 of the first pair is arranged around the firstelectrode 106. The first electrode 106 of the first pair is electricallyconnected to the first balanced terminal 211 of the first balun 103, andthe second electrode 135 of the first pair is electrically connected tothe second balanced terminal 212 of the first balun 103. The firstelectrode 141 of the second pair holds the substrate 112. The secondelectrode 145 of the second pair is arranged around the first electrode141. The first electrode 141 of the second pair is electricallyconnected to the first balanced terminal 411 of the second balun 303,and the second electrode 145 of the second pair is electricallyconnected to the second balanced terminal 412 of the second balun 303.

The above arrangement can be understood as an arrangement in which thefirst electrode 106 of the first pair is electrically connected to thefirst terminal 251, the second electrode 135 of the first pair iselectrically connected to the second terminal 252, the first terminal251 is electrically connected to the first balanced terminal 211 of thefirst balun 103, and the second terminal 252 is electrically connectedto the second balanced terminal 212 of the first balun 103. The abovearrangement can be understood as an arrangement in which the firstelectrode 141 of the second pair is electrically connected to the thirdterminal 451, the second electrode 145 of the second pair iselectrically connected to the fourth terminal 452, the third terminal451 is electrically connected to the first balanced terminal 411 of thesecond balun 303, and the fourth terminal 452 is electrically connectedto the second balanced terminal 412 of the second balun 303.

The first electrode 106 of the first pair and the first balancedterminal 211 (first terminal 251) of the first balun 103 canelectrically be connected via a blocking capacitor 104. The blockingcapacitor 104 blocks a DC current between the first balanced terminal211 of the first balun 103 and the first electrode 106 of the first pair(or between the first balanced terminal 211 and the second balancedterminal 212 of the first balun 103). Instead of providing the blockingcapacitor 104, a first impedance matching circuit 102 may be configuredto block a DC current flowing between the first unbalanced terminal 201and the second unbalanced terminal 202 of the first balun 103. The firstelectrode 106 and the second electrode 135 of the first pair can besupported by the vacuum container 110 via an insulator 132.

The first electrode 141 of the second pair and the first balancedterminal 411 (third terminal 451) of the second balun 303 canelectrically be connected via a blocking capacitor 304. The blockingcapacitor 304 blocks a DC current between the first balanced terminal411 of the second balun 303 and the first electrode 141 of the secondpair (or between the first balanced terminal 411 and the second balancedterminal 412 of the second balun 303). Instead of providing the blockingcapacitor 304, a second impedance matching circuit 302 may be configuredto block a DC current flowing between the first unbalanced terminal 201and the second unbalanced terminal 202 of the second balun 303. Thefirst electrode 141 and the second electrode 145 of the second pair canbe supported by the vacuum container 110 via an insulator 142.

The plasma processing apparatus 1 can include a first high-frequencypower supply 101, and the first impedance matching circuit 102 arrangedbetween the first high-frequency power supply 101 and the first balun103. The first high-frequency power supply 101 supplies a high frequencybetween the first unbalanced terminal 201 and the second unbalancedterminal 202 of the first balun 103 via the first impedance matchingcircuit 102. In other words, the first high-frequency power supply 101supplies a high frequency between the first electrode 106 and the secondelectrode 135 via the first impedance matching circuit 102, the firstbalun 103, and the blocking capacitor 104. Alternatively, the firsthigh-frequency power supply 101 supplies a high frequency between thefirst terminal 251 and the second terminal 252 of the main body 10 viathe first impedance matching circuit 102 and the first balun 103. Thefirst balun 103 and the first electrode 106 and the second electrode 135of the first pair form the first high-frequency supply unit thatsupplies a high frequency to the internal space of the vacuum container110.

The plasma processing apparatus 1 can include a second high-frequencypower supply 301, and the second impedance matching circuit 302 arrangedbetween the second high-frequency power supply 301 and the second balun303. The second high-frequency power supply 301 supplies a highfrequency between the first unbalanced terminal 401 and the secondunbalanced terminal 402 of the second balun 303 via the second impedancematching circuit 302. In other words, the second high-frequency powersupply 301 supplies a high frequency between the first electrode 141 andthe second electrode 145 of the second pair via the second impedancematching circuit 302, the second balun 303, and the blocking capacitor304. Alternatively, the second high-frequency power supply 301 suppliesa high frequency between the third terminal 451 and the fourth terminal452 of the main body 10 via the second impedance matching circuit 302and the second balun 303. The second balun 303 and the first electrode141 and the second electrode 145 of the second pair form the secondhigh-frequency supply unit that supplies a high frequency to theinternal space of the vacuum container 110.

Let Rp1−jXp1 be an impedance when viewing the side of the firstelectrode 106 and the second electrode 135 of the first pair (the sideof the main body 10) from the side of the first balanced terminal 211and the second balanced terminal 212 of the first balun 103 in a statein which plasma is generated in the internal space of the vacuumcontainer 110 by supplying a high frequency from the firsthigh-frequency power supply 101. Let X1 be the reactance component(inductance component) of the impedance of a first coil 221 of the firstbalun 103. In this definition, satisfying 1.5≤X1/Rp1≤5000 isadvantageous in stabilizing the potential of the plasma formed in theinternal space of the vacuum container 110.

In addition, let Rp2−jXp2 be an impedance when viewing the side of thefirst electrode 141 and the second electrode 145 of the second pair (theside of the main body 10) from the side of the first balanced terminal411 and the second balanced terminal 412 of the second balun 303 in astate in which plasma is generated in the internal space of the vacuumcontainer 110 by supplying a high frequency from the secondhigh-frequency power supply 301. Let X2 be the reactance component(inductance component) of the impedance of the first coil 221 of thesecond balun 303. In this definition, satisfying 1.5≤X2/Rp2≤5000 isadvantageous in stabilizing the potential of the plasma formed in theinternal space of the vacuum container 110.

FIG. 11 schematically shows the arrangement of a plasma processingapparatus 1 according to the fifth embodiment of the present invention.The apparatus 1 according to the fifth embodiment has an arrangementobtained by adding driving mechanisms 114 and 314 to the plasmaprocessing apparatus 1 according to the fourth embodiment. The drivingmechanism 114 can include at least one of a mechanism for verticallymoving a first electrode 141 and a mechanism for rotating the firstelectrode 141. The driving mechanism 314 can include a mechanism forvertically moving a second electrode 145.

FIG. 12 schematically shows the arrangement of a plasma processingapparatus 1 according to the sixth embodiment of the present invention.The plasma processing apparatus according to the sixth embodiment canoperate as a sputtering apparatus that forms a film on a substrate 112by sputtering. Items which are not referred to as the sixth embodimentcan comply with the first to fifth embodiments. The plasma processingapparatus 1 according to the sixth embodiment includes a plurality offirst high-frequency supply units and at least one second high-frequencysupply unit. One of the plurality of first high-frequency supply unitscan include a first electrode 106 a, a second electrode 135 a, and afirst balun 103 a. Another one of the plurality of first high-frequencysupply units can include a first electrode 106 b, a second electrode 135b, and a first balun 103 b. An example in which the plurality of firsthigh-frequency supply units are formed by two high-frequency supplyunits will be described. In addition, the two high-frequency supplyunits and constituent elements associated with them are distinguishedfrom each other using subscripts a and b. Similarly, two targets aredistinguished from each other using subscripts a and b.

From another viewpoint, the plasma processing apparatus 1 includes theplurality of first baluns 103 a and 103 b, a second balun 303, a vacuumcontainer 110, the first electrode 106 a and the second electrode 135 a,the first electrode 106 b and the second electrode 135 b, and a firstelectrode 141 and a second electrode 145. Alternatively, it may beunderstood that the plasma processing apparatus 1 includes the pluralityof first baluns 103 a and 103 b, the second balun 303, and a main body10, and the main body 10 includes the vacuum container 110, the firstelectrode 106 a and the second electrode 135 a, the first electrode 106b and the second electrode 135 b, and the first electrode 141 and thesecond electrode 145. The main body 10 includes first terminals 251 aand 251 b, second terminals 252 a and 252 b, a third terminal 451, and afourth terminal 452.

The first balun 103 a includes a first unbalanced terminal 201 a, asecond unbalanced terminal 202 a, a first balanced terminal 211 a, and asecond balanced terminal 212 a. An unbalanced circuit is connected tothe first unbalanced terminal 201 a and the second unbalanced terminal202 a of the first balun 103 a, and a balanced circuit is connected tothe first balanced terminal 211 a and the second balanced terminal 212 aof the first balun 103 a. The first balun 103 b includes a firstunbalanced terminal 201 b, a second unbalanced terminal 202 b, a firstbalanced terminal 211 b, and a second balanced terminal 212 b. Anunbalanced circuit is connected to the first unbalanced terminal 201 band the second unbalanced terminal 202 b of the first balun 103 b, and abalanced circuit is connected to the first balanced terminal 211 b andthe second balanced terminal 212 b of the first balun 103 b.

The second balun 303 can have an arrangement similar to that of thefirst balun 103 a or 103 b. The second balun 303 includes a firstunbalanced terminal 401, a second unbalanced terminal 402, a firstbalanced terminal 411, and a second balanced terminal 412. An unbalancedcircuit is connected to the first unbalanced terminal 401 and the secondunbalanced terminal 402 of the second balun 303, and a balanced circuitis connected to the first balanced terminal 411 and the second balancedterminal 412 of the second balun 303. The vacuum container 110 isgrounded.

The first electrodes 106 a and 106 b hold targets 109 a and 109 b,respectively. Each of the targets 109 a and 109 b can be, for example,an insulator material or a conductor material. The second electrodes 135a and 135 b are arranged around the first electrodes 106 a and 106 b,respectively. The first electrodes 106 a and 106 b are electricallyconnected to the first balanced terminals 211 a and 211 b of the firstbaluns 103 a and 103 b, respectively, and the second electrodes 135 aand 135 b are electrically connected to the second balanced terminals212 a and 212 b of the first baluns 103 a and 103 b, respectively.

The first electrode 141 holds the substrate 112. The second electrode145 is arranged around the first electrode 141. The first electrode 141is electrically connected to the first balanced terminal 411 of thesecond balun 303, and the second electrode 145 is electrically connectedto the second balanced terminal 412 of the second balun 303.

The above arrangement can be understood as an arrangement in which thefirst electrodes 106 a and 106 b are electrically connected to the firstterminals 251 a and 251 b, respectively, the second electrodes 135 a and135 b are electrically connected to the second terminals 252 a and 252b, respectively, the first terminals 251 a and 251 b are electricallyconnected to the first balanced terminals 211 a and 111 b of the firstbaluns 103 a and 103 b, respectively, and the second terminals 252 a and252 b are electrically connected to the second balanced terminals 212 aand 212 b of the first baluns 103 a and 103 b, respectively. The abovearrangement can be understood as an arrangement in which the firstelectrode 141 is electrically connected to the third terminal 451, thesecond electrode 145 is electrically connected to the fourth terminal452, the third terminal 451 is electrically connected to the firstbalanced terminal 411 of the second balun 303, and the fourth terminal452 is electrically connected to the second balanced terminal 412 of thesecond balun 303.

The first electrodes 106 a and 106 b and the first balanced terminals211 a and 211 b (first terminals 251 a and 251 b) of the first baluns103 a and 103 b can electrically be connected via blocking capacitors104 a and 104 b, respectively. The blocking capacitors 104 a and 104 bblock DC currents between the first electrodes 106 a and 106 b and thefirst balanced terminals 211 a and 211 b of the first baluns 103 a and103 b (or between the first balanced terminals 211 a and 211 b and thesecond balanced terminals 212 a and 212 b of the first baluns 103 a and103 b), respectively. Instead of providing the blocking capacitors 104 aand 104 b , first impedance matching circuits 102 a and 102 b may beconfigured to block DC currents flowing between the first unbalancedterminals 201 a and 201 b and the second unbalanced terminals 202 a and202 b of the first baluns 103 a and 103 b, respectively. Alternatively,the blocking capacitors 104 a and 104 b may be arranged between thesecond electrodes 135 a and 135 b and the second balanced terminals 212a and 212 b (second terminals 252 a and 252 b) of the first baluns 103 aand 103 b, respectively. The first electrodes 106 a and 106 b and thesecond electrodes 135 a and 135 b can be supported by the vacuumcontainer 110 via insulators 132 a and 132 b, respectively.

The first electrode 141 and the first balanced terminal 411 (thirdterminal 451) of the second balun 303 can electrically be connected viaa blocking capacitor 304. The blocking capacitor 304 blocks a DC currentbetween the first electrode 141 and the first balanced terminal 411 ofthe second balun 303 (or between the first balanced terminal 411 and thesecond balanced terminal 412 of the second balun 303). Instead ofproviding the blocking capacitor 304, a second impedance matchingcircuit 302 may be configured to block a DC current flowing between thefirst unbalanced terminal 201 and the second unbalanced terminal 202 ofthe second balun 303. Alternatively, the blocking capacitor 304 may bearranged between the second electrode 145 and the second balancedterminal 412 (fourth terminal 452) of the second balun 303. The firstelectrode 141 and the second electrode 145 can be supported by thevacuum container 110 via an insulator 142.

The plasma processing apparatus 1 can include a plurality of firsthigh-frequency power supplies 101 a and 101 b, and the first impedancematching circuits 102 a and 102 b respectively arranged between theplurality of first high-frequency power supplies 101 a and 101 b and theplurality of first baluns 103 a and 103 b. The first high-frequencypower supplies 101 a and 101 b supply high frequencies between the firstunbalanced terminals 201 a and 201 b and the second unbalanced terminals202 a and 202 b of the first baluns 103 a and 103 b via the firstimpedance matching circuits 102 a and 102 b, respectively. In otherwords, the first high-frequency power supplies 101 a and 101 b supplyhigh frequencies between the first electrodes 106 a and 106 b and thesecond electrodes 135 a and 135 b via the first impedance matchingcircuits 102 a and 102 b, the first baluns 103 a and 103 b, and theblocking capacitors 104 a and 104 b, respectively. Alternatively, thefirst high-frequency power supplies 101 a and 101 b; supply highfrequencies between the first terminals 251 a and 251 b and the secondterminals 252 a and 252 b of the main body 10 via the first impedancematching circuits 102 a and 101 b and the first baluns 103 a and 103 b.

The plasma processing apparatus 1 can include a second high-frequencypower supply 301, and the second impedance matching circuit 302 arrangedbetween the second high-frequency power supply 301 and the second balun303. The second high-frequency power supply 301 supplies a highfrequency between the first unbalanced terminal 401 and the secondunbalanced terminal 402 of the second balun 303 via the second impedancematching circuit 302. In other words, the second high-frequency powersupply 301 supplies a high frequency between the first electrode 141 andthe second electrode 145 via the second impedance matching circuit 302,the second balun 303, and the blocking capacitor 304. Alternatively, thesecond high-frequency power supply 301 supplies a high frequency betweenthe third terminal 451 and the fourth terminal 452 of the main body 10via the second impedance matching circuit 302 and the second balun 303.

FIG. 13 schematically shows the arrangement of a plasma processingapparatus 1 according to the seventh embodiment of the presentinvention. The plasma processing apparatus according to the seventhembodiment can operate as a sputtering apparatus that forms a film on asubstrate 112 by sputtering. Items which are not referred to as theplasma processing apparatus 1 according to the seventh embodiment cancomply with the first to sixth embodiments. The plasma processingapparatus 1 includes a first balun 103, a second balun 303, a vacuumcontainer 110, a first electrode 105 a and a second electrode 105 bconstituting the first pair, and a first electrode 141 and a secondelectrode 145 constituting the second pair. Alternatively, it may beunderstood that the plasma processing apparatus 1 includes the firstbalun 103, the second balun 303, and a main body 10, and the main body10 includes the vacuum container 110, the first electrode 105 a and thesecond electrode 105 b constituting the first pair, and the firstelectrode 141 and the second electrode 145 constituting the second pair.The main body 10 includes a first terminal 251, a second terminal 252, athird terminal 451 and a fourth terminal 452.

The first balun 103 includes a first unbalanced terminal 201, a secondunbalanced terminal 202, a first balanced terminal 211, and a secondbalanced terminal 212. An unbalanced circuit is connected to the firstunbalanced terminal 201 and the second unbalanced terminal 202 of thefirst balun 103, and a balanced circuit is connected to the firstbalanced terminal 211 and the second balanced terminal 212 of the firstbalun 103. The second balun 303 can have an arrangement similar to thatof the first balun 103. The second balun 303 includes a first unbalancedterminal 401, a second unbalanced terminal 402, a first balancedterminal 411, and a second balanced terminal 412. An unbalanced circuitis connected to the first unbalanced terminal 401 and the secondunbalanced terminal 402 of the second balun 303, and a balanced circuitis connected to the first balanced terminal 411 and the second balancedterminal 412 of the second balun 303. The vacuum container 110 isgrounded.

The first electrode 105 a of the first pair holds a first target 109 a,and opposes a space on the side of the substrate 112 via the firsttarget 109 a. The second electrode 105 b of the first pair is arrangedadjacent to the first electrode 105 a, holds a second target 105 b, andopposes the space on the side of the substrate 112 via the second target109 b. Each of the targets 109 a and 109 b can be, for example, aninsulator material or a conductor material. The first electrode 105 a ofthe first pair is electrically connected to the first balanced terminal211 of the first balun 103, and the second electrode 105 b of the firstpair is electrically connected to the second balanced terminal 212 ofthe first balun 103.

The first electrode 141 of the second pair holds the substrate 112. Thesecond electrode 145 of the second pair is arranged around the firstelectrode 141. The first electrode 141 of the second pair iselectrically connected to the first balanced terminal 411 of the secondbalun 303, and the second electrode 145 of the second pair iselectrically connected to the second balanced terminal 412 of the secondbalun 303.

The above arrangement can be understood as an arrangement in which thefirst electrode 105 a of the first pair is electrically connected to thefirst terminal 251, the second electrode 105 b of the first pair iselectrically connected to the second terminal 252, the first terminal251 is electrically connected to the first balanced terminal 211 of thefirst balun 103, and the second terminal 252 is connected to the secondbalanced terminal 212 of the first balun 103. Furthermore, the abovearrangement can be understood as an arrangement in which the firstelectrode 141 of the second pair is electrically connected to the thirdterminal 451, the second electrode 145 of the second pair iselectrically connected to the fourth terminal 452, the third terminal451 is electrically connected to the first balanced terminal 411 of thesecond balun 303, and the fourth terminal 452 is connected to the secondbalanced terminal 412 of the second balun 303.

The first electrode 105 a of the first pair and the first balancedterminal 211 (first terminal 251) of the first balun 103 canelectrically be connected via a blocking capacitor 104 a. The blockingcapacitor 104 a blocks a DC current between the first balanced terminal211 of the first balun 103 and the first electrode 105 a of the firstpair (or between the first balanced terminal 211 and the second balancedterminal 212 of the first balun 103). The second electrode 105 b of thefirst pair and the second balanced terminal 212 (second terminal 252) ofthe first balun 103 can electrically be connected via a blockingcapacitor 104 b. The blocking capacitor 104 b blocks a DC currentbetween the second balanced terminal 212 of the first balun 103 and thesecond electrode 105 b of the first pair (or between the first balancedterminal 211 and the second balanced terminal 212 of the first balun103). The first electrode 105 a and the second electrode 105 b of thefirst pair can be supported by the vacuum container 110 via insulators132 a and 132 b, respectively.

The first electrode 141 of the second pair and the first balancedterminal 411 (third terminal 451) of the second balun 303 canelectrically be connected via a blocking capacitor 304. The blockingcapacitor 304 blocks a DC current between the first balanced terminal411 of the second balun 303 and the first electrode 141 of the secondpair (or between the first balanced terminal 411 and the second balancedterminal 412 of the second balun 303). Instead of providing the blockingcapacitor 304, a second impedance matching circuit 302 may be configuredto block a DC current flowing between the first unbalanced terminal 401and the second unbalanced terminal 402 of the second balun 303. Thefirst electrode 141 and the second electrode 145 of the second pair canbe supported by the vacuum container 110 via insulators 142 and 146,respectively.

The plasma processing apparatus 1 can include a first high-frequencypower supply 101, and a first impedance matching circuit 102 arrangedbetween the first high-frequency power supply 101 and the first balun103. The first high-frequency power supply 101 supplies a high frequencybetween the first electrode 105 a and the second electrode 105 b via thefirst impedance matching circuit 102, the first balun 103, and theblocking capacitors 104 a and 104 b. Alternatively, the firsthigh-frequency power supply 101 supplies a high frequency between thefirst terminal 251 and the second terminal 252 of the main body 10 viathe first impedance matching circuit 102 and the first balun 103. Thefirst balun 103 and the first electrode 105 a and the second electrode105 b of the first pair form the first high-frequency supply unit thatsupplies a high frequency to the internal space of the vacuum container110.

The plasma processing apparatus 1 can include a second high-frequencypower supply 301, and the second impedance matching circuit 302 arrangedbetween the second high-frequency power supply 301 and the second balun303. The second high-frequency power supply 301 supplies a highfrequency between the first unbalanced terminal 401 and the secondunbalanced terminal 402 of the second balun 303 via the second impedancematching circuit 302. The second high-frequency power supply 301supplies a high frequency between the first electrode 141 and the secondelectrode 145 of the second pair via the second impedance matchingcircuit 302, the second balun 303, and the blocking capacitor 304.Alternatively, the second high-frequency power supply 301 supplies ahigh frequency between the third terminal 451 and the fourth terminal452 of the main body 10 via the second impedance matching circuit 302and the second balun 303. The second balun 303 and the first electrode141 and the second electrode 145 of the second pair form the secondhigh-frequency supply unit that supplies a high frequency to theinternal space of the vacuum container 110.

Let Rp1−jXp1 be an impedance when viewing the side of the firstelectrode 105 a and the second electrode 105 b of the first pair (theside of the main body 10) from the side of the first balanced terminal211 and the second balanced terminal 212 of the first balun 103 in astate in which plasma is generated in the internal space of the vacuumcontainer 110 by supplying a high frequency from the firsthigh-frequency power supply 101. Let X1 be the reactance component(inductance component) of the impedance of a first coil 221 of the firstbalun 103. In this definition, satisfying 1.5≤X1/Rp1≤5000 isadvantageous in stabilizing the potential of the plasma formed in theinternal space of the vacuum container 110.

In addition, let Rp2−jXp2 be an impedance when viewing the side of afirst electrode 127 and a second electrode 130 of the second pair (theside of the main body 10) from the side of the first balanced terminal411 and the second balanced terminal 412 of the second balun 303 in astate in which plasma is generated in the internal space of the vacuumcontainer 110 by supplying a high frequency from the secondhigh-frequency power supply 301. Let X2 be the reactance component(inductance component) of the impedance of a first coil 221 of thesecond balun 303. In this definition, satisfying 1.5≤X2/Rp2≤5000 isadvantageous in stabilizing the potential of the plasma formed in theinternal space of the vacuum container 110.

The plasma processing apparatus 1 according to the seventh embodimentcan further include at least one of a mechanism for vertically movingthe first electrode 141 constituting the second pair and a mechanism forrotating the first electrode 141 constituting the second pair. In theexample shown in FIG. 13 , the plasma processing apparatus 1 includes adriving mechanism 114 having both the mechanism for vertically movingthe first electrode 141 and the mechanism for rotating the firstelectrode 141. Furthermore, in the example shown in FIG. 13 , the plasmaprocessing apparatus 1 includes a mechanism 314 for vertically movingthe second electrode 145 constituting the second pair. Bellows formingvacuum partitions can be provided between the vacuum container 110 andthe driving mechanisms 114 and 314.

The function of the first balun 103 in the plasma processing apparatus 1according to the seventh embodiment shown in FIG. 13 will be describedwith reference to FIG. 14 . Let I1 be a current flowing through thefirst unbalanced terminal 201, I2 be a current flowing through the firstbalanced terminal 211, I2′ be a current flowing through the secondunbalanced terminal 202, and I3 be a current, of the current I2, flowingto ground. When I3=0, that is, no current flows to ground on thebalanced circuit side, the isolation performance of the balanced circuitwith respect to ground is highest. When I3=I2, that is, all the current12 flowing through the first balanced terminal 211 flows to ground, theisolation performance of the balanced circuit with respect to ground islowest. Similar to the first to fifth embodiments, an index ISOrepresenting the degree of the isolation performance is given by anequation below. Under this definition, as the absolute value of theindex ISO is larger, the isolation performance is higher.ISO [dB]=20 log(I3/I2′)

In FIG. 14 , Rp−jXp (=Rp/2−jXp/2+Rp/2−jXp/2) represents an impedance(including the reactances of the blocking capacitors 104 a and 104 b)when viewing the side of the first electrode 105 a and the secondelectrode 105 b (the side of the main body 10) from the side of thefirst balanced terminal 211 and the second balanced terminal 212 in astate in which plasma is generated in the internal space of the vacuumcontainer 110. Rp represents a resistance component, and −Xp representsa reactance component. Furthermore, in FIG. 14 , X represents thereactance component (inductance component) of the impedance of the firstcoil 221 of the balun 103. ISO has a correlation with X/Rp.

FIG. 4 referred to in the description of the first embodimentexemplifies the relationship among the currents I1 (=I2), I2′, and I3,ISO, and α (=X/Rp). The relationship shown in FIG. 4 also holds in theseventh embodiment. The present inventor found that in the seventhembodiment as well, satisfying 1.5≤X/Rp≤5000 is advantageous in makingthe potential (plasma potential) of plasma formed in the internal space(the space between the first electrode 105 a and the second electrode105 b) of the vacuum container 110 insensitive to the state of the innersurface of the vacuum container 110. When the plasma potential isinsensitive to the state of the inner surface of the vacuum container110, this indicates that it is possible to stabilize the plasmapotential even if the plasma processing apparatus 1 is used for a longperiod. 1.5≤X/Rp≤5000 corresponds to −10.0 dB≥ISO≥=80 dB.

FIGS. 15A to 15D each show the plasma potential, the potential (cathode1 potential) of the first electrode 105 a, and the potential (cathode 2potential) of the second electrode 105 b when 1.5≤X/Rp≤5000 issatisfied. FIG. 15A shows the plasma potential, the potential (cathode 1potential) of the first electrode 105 a, and the potential (cathode 2potential) of the second electrode 105 b in a state in which a resistivefilm (1 mΩ) is formed on the inner surface of the vacuum container 110.FIG. 15B shows the plasma potential, the potential (cathode 1 potential)of the first electrode 105 a, and the potential (cathode 2 potential) ofthe second electrode 105 b in a state in which a resistive film (1,000Ω) is formed on the inner surface of the vacuum container 110. FIG. 15Cshows the plasma potential, the potential (cathode 1 potential) of thefirst electrode 105 a, and the potential (cathode 2 potential) of thesecond electrode 105 b in a state in which an inductive film (0.6 μH) isformed on the inner surface of the vacuum container 110. FIG. 15D showsthe plasma potential, the potential (cathode 1 potential) of the firstelectrode 105 a, and the potential (cathode 2 potential) of the secondelectrode 105 b in a state in which a capacitive film (0.1 nF) is formedon the inner surface of the vacuum container 110. With reference toFIGS. 15A to 15D, it is understood that satisfying 1.5≤X/Rp≤5000 isadvantageous in stabilizing the plasma potential in various states ofthe inner surface of the vacuum container 110.

FIGS. 16A to 16D each show a result of simulating the plasma potential,the potential (cathode 1 potential) of the first electrode 105 a, andthe potential (cathode 2 potential) of the second electrode 105 b when1.5≤X/Rp≤5000 is not satisfied. FIG. 16A shows the plasma potential, thepotential (cathode 1 potential) of the first electrode 105 a, and thepotential (cathode 2 potential) of the second electrode 105 b in a statein which a resistive film (1 mΩ) is formed on the inner surface of thevacuum container 110. FIG. 16B shows the plasma potential, the potential(cathode 1 potential) of the first electrode 105 a, and the potential(cathode 2 potential) of the second electrode 105 b in a state in whicha resistive film (1,000 Ω) is formed on the inner surface of the vacuumcontainer 110. FIG. 16C shows the plasma potential, the potential(cathode 1 potential) of the first electrode 105 a, and the potential(cathode 2 potential) of the second electrode 105 b in a state in whichan inductive film (0.6 μH) is formed on the inner surface of the vacuumcontainer 110. FIG. 16D shows the plasma potential, the potential(cathode 1 potential) of the first electrode 105 a, and the potential(cathode 2 potential) of the second electrode 105 b in a state in whicha capacitive film (0.1 nF) is formed on the inner surface of the vacuumcontainer 110. With reference to FIGS. 16A to 16D, it is understood thatwhen 1.5≤X/Rp≤5000 is not satisfied, the plasma potential changesdepending on the state of the inner surface of the vacuum container 110.

In both the case in which X/Rp>5000 (for example, X/Rp=∞) is satisfiedand the case in which X/Rp<1.5 (for example, X/Rp=1.16 or X/Rp=0.87) issatisfied, the plasma potential readily changes depending on the stateof the inner surface of the vacuum container 110. If X/Rp>5000 issatisfied, in a state in which no film is formed on the inner surface ofthe vacuum container 110, discharge occurs only between the firstelectrode 105 a and the second electrode 105 b. However, if X/Rp>5000 issatisfied, when a film starts to be formed on the inner surface of thevacuum container 110, the plasma potential sensitively reacts to this,and the results exemplified in FIGS. 16A to 16D are obtained. On theother hand, when X/Rp<1.5 is satisfied, a current flowing to ground viathe vacuum container 110 is large. Therefore, the influence of the stateof the inner surface of the vacuum container 110 (the electricalcharacteristic of a film formed on the inner surface) is conspicuous,and the plasma potential changes depending on formation of a film. Thus,as described above, the plasma processing apparatus 1 is advantageouslyconfigured to satisfy 1.5≤X/Rp≤5000.

FIG. 17 schematically shows the arrangement of a plasma processingapparatus 1 according to the eighth embodiment of the present invention.The plasma processing apparatus according to the eighth embodiment canoperate as a sputtering apparatus that forms a film on a substrate 112by sputtering. Items which are not referred to as the plasma processingapparatus 1 according to the eighth embodiment can comply with the firstto seventh embodiments. The plasma processing apparatus 1 according tothe eighth embodiment includes a balun (first balun) 103, a vacuumcontainer 110, a first electrode 105 a, a second electrode 105 b, and aground electrode 400. Alternatively, it may be understood that theplasma processing apparatus 1 includes the balun 103 and a main body 10,and the main body 10 includes the vacuum container 110, the firstelectrode 105 a, the second electrode 105 b, and the ground electrode400. The main body 10 includes a first terminal 251 and a secondterminal 252.

The ground electrode 400 is arranged in the vacuum container 110, andgrounded. The ground electrode 400 can include a plurality of plateportions PLT arranged to be parallel to each other. The plurality ofplate portions PLT can be arranged so that the ground electrode 400 hasa comb-tooth shape in one section (for example, a section along thevertical direction). From another viewpoint, the ground electrode 400can have a comb-tooth shape in one section (for example, a section alongthe vertical direction). This arrangement of the ground electrode 400can contribute to an increase in area of a portion functioning as ananode. Furthermore, this arrangement of the ground electrode 400 isadvantageous in suppressing formation of a film on the ground electrode400 when forming a film on the substrate 112.

The first electrode 105 a can include a first holding surface HS1 thatholds a first target 109 a as the first member, and the second electrode105 b can include a second holding surface HS2 that holds a secondtarget 109 b as the second member. The first holding surface HS1 and thesecond holding surface HS2 can belong to one plane PL. The groundelectrode 400 can be arranged to intersect the plane PL. The groundelectrode 400 can include, for example, a portion arranged between thefirst electrode 105 a and the second electrode 105 b. The groundelectrode 400 can include, for example, a portion arranged between thefirst target 109 a as the first member and the second target 109 b asthe second member. The ground electrode 400 is advantageous insuppressing formation of a film on the ground electrode 400 when forminga film on the substrate 112.

The plasma processing apparatus 1 according to the eighth embodiment mayfurther include a second balun 303, a third electrode 141, and a fourthelectrode 145. In other words, the plasma processing apparatus 1 caninclude the first balun 103, the second balun 303, the vacuum container110, the first electrode 105 a, the second electrode 105 b, the thirdelectrode 141, and the fourth electrode 145. Alternatively, it may beunderstood that the plasma processing apparatus 1 includes the firstbalun 103, the second balun 303, and the main body 10, and the main body10 includes the vacuum container 110, the first electrode 105 a, thesecond electrode 105 b, the third electrode 141, and the fourthelectrode 145. The third electrode 141 and the fourth electrode 145 arearranged to oppose the plane PL. The main body 10 includes the firstterminal 251, the second terminal 252, a third terminal 451, and afourth terminal 452.

The first balun 103 includes a first unbalanced terminal 201, a secondunbalanced terminal 202, a first balanced terminal 211, and a secondbalanced terminal 212. An unbalanced circuit is connected to the firstunbalanced terminal 201 and the second unbalanced terminal 202 of thefirst balun 103, and a balanced circuit is connected to the firstbalanced terminal 211 and the second balanced terminal 212 of the firstbalun 103. The second balun 303 can have an arrangement similar to thatof the first balun 103. The second balun 303 includes a third unbalancedterminal 401, a fourth unbalanced terminal 402, a third balancedterminal 411, and a fourth balanced terminal 412. An unbalanced circuitis connected to the third unbalanced terminal 401 and the fourthunbalanced terminal 402 of the second balun 303, and a balanced circuitis connected to the third balanced terminal 411 and the fourth balancedterminal 412 of the second balun 303. The vacuum container 110 isgrounded. Each of the baluns 103 and 303 can have the arrangement shownin FIG. 2A or 2B (FIG. 14 ).

The first electrode 105 a holds the first target 109 a, and opposes aspace on the side of the substrate 112 as a processing target via thefirst target 109 a. The second electrode 105 b is arranged adjacent tothe first electrode 105 a, holds the second target 109 b, and opposesthe space on the side of the substrate 112 as a processing target viathe second target 109 b. Each of the targets 109 a and 109 b can be, forexample, an insulator material or a conductor material. The firstelectrode 105 a is electrically connected to the first balanced terminal211 of the first balun 103, and the second electrode 105 b iselectrically connected to the second balanced terminal 212 of the firstbalun 103.

The third electrode 141 holds the substrate 112. The fourth electrode145 can be arranged around the third electrode 141. The third electrode141 is electrically connected to the first balanced terminal 411 of thesecond balun 303, and the fourth electrode 145 is electrically connectedto the second balanced terminal 412 of the second balun 303.

The above arrangement can be understood as an arrangement in which thefirst electrode 105 a is electrically connected to the first terminal251, the second electrode 105 b is electrically connected to the secondterminal 252, the first terminal 251 is electrically connected to thefirst balanced terminal 211 of the first balun 103, and the secondterminal 252 is connected to the second balanced terminal 212 of thefirst balun 103. The above arrangement can be understood as anarrangement in which the third electrode 141 is electrically connectedto the third terminal 451, the fourth electrode 145 is electricallyconnected to the fourth terminal 452, the third terminal 451 iselectrically connected to the first balanced terminal 411 of the secondbalun 303, and the fourth terminal 452 is connected to the secondbalanced terminal 412 of the second balun 303.

The first electrode 105 a and the first balanced terminal 211 (firstterminal 251) of the first balun 103 can electrically be connected via ablocking capacitor 104 a. The blocking capacitor 104 a blocks a DCcurrent between the first balanced terminal 211 of the first balun 103and the first electrode 105 a (or between the first balanced terminal211 and the second balanced terminal 212 of the first balun 103). Thesecond electrode 105 b and the second balanced terminal 212 (secondterminal 252) of the first balun 103 can electrically be connected via ablocking capacitor 104 b. The blocking capacitor 104 b blocks a DCcurrent between the second balanced terminal 212 of the first balun 103and the second electrode 105 b (or between the first balanced terminal211 and the second balanced terminal 212 of the first balun 103). Thefirst electrode 105 a and the second electrode 105 b can be supported bythe vacuum container 110 via insulators 132 a and 132 b, respectively.

The third electrode 141 and the first balanced terminal 411 (thirdterminal 451) of the second balun 303 can electrically be connected viaa blocking capacitor 304. The blocking capacitor 304 blocks a DC currentbetween the first balanced terminal 411 of the second balun 303 and thethird electrode 141 (or between the first balanced terminal 411 and thesecond balanced terminal 412 of the second balun 303). Instead ofproviding the blocking capacitor 304, a second impedance matchingcircuit 302 may be configured to block a DC current flowing between thefirst unbalanced terminal 401 and the second unbalanced terminal 402 ofthe second balun 303. The third electrode 141 and the fourth electrode145 can be supported by the vacuum container 110 via insulators 142 and146, respectively.

The plasma processing apparatus 1 can include a first high-frequencypower supply 101, and a first impedance matching circuit 102 arrangedbetween the first high-frequency power supply 101 and the first balun103. The first high-frequency power supply 101 supplies a high frequencybetween the first electrode 105 a and the second electrode 105 b via thefirst impedance matching circuit 102, the first balun 103, and theblocking capacitors 104 a and 104 b. Alternatively, the firsthigh-frequency power supply 101 supplies a high frequency between thefirst terminal 251 and the second terminal 252 of the main body 10 viathe first impedance matching circuit 102 and the first balun 103. Thefirst balun 103, the first electrode 105 a, and the second electrode 105b form the first high-frequency supply unit that supplies a highfrequency to the internal space of the vacuum container 110.

The plasma processing apparatus 1 can include a second high-frequencypower supply 301, and the second impedance matching circuit 302 arrangedbetween the second high-frequency power supply 301 and the second balun303. The second high-frequency power supply 301 supplies a highfrequency between the first unbalanced terminal 401 and the secondunbalanced terminal 402 of the second balun 303 via the second impedancematching circuit 302. The second high-frequency power supply 301supplies a high frequency between the third electrode 141 and the fourthelectrode 145 via the second impedance matching circuit 302, the secondbalun 303, and the blocking capacitor 304. Alternatively, the secondhigh-frequency power supply 301 supplies a high frequency between thethird terminal 451 and the fourth terminal 452 of the main body 10 viathe second impedance matching circuit 302 and the second balun 303. Thesecond balun 303, the third electrode 141, and the fourth electrode 145form the second high-frequency supply unit that supplies a highfrequency to the internal space of the vacuum container 110.

Let Rp1−jXp1 be an impedance when viewing the side of the firstelectrode 105 a and the second electrode 105 b (the side of the mainbody 10) from the side of the first balanced terminal 211 and the secondbalanced terminal 212 of the first balun 103 in a state in which plasmais generated in the internal space of the vacuum container 110 bysupplying a high frequency from the first high-frequency power supply101. Let X1 be the reactance component (inductance component) of theimpedance of a first coil 221 of the first balun 103. In thisdefinition, satisfying 1.5≤X1/Rp1≤5000 is advantageous in stabilizingthe potential of the plasma formed in the internal space of the vacuumcontainer 110. Note that satisfying the condition of 1.5≤X/Rp1≤5000 isnot essential to the eighth embodiment and is an advantageous condition.In the eighth embodiment, even if the condition of 1.5≤X/Rp1≤5000 is notsatisfied, it is possible to obtain the effect of making the potential(plasma potential) of the plasma formed in the internal space (the spacebetween the first electrode 106 and the second electrode 111) of thevacuum container 110 insensitive to the state of the inner surface ofthe vacuum container 110 by providing the ground electrode 400 in thevacuum container 110.

In addition, let Rp2−jXp2 be an impedance when viewing the side of thethird electrode 141 and the fourth electrode 145 (the side of the mainbody 10) from the side of the first balanced terminal 411 and the secondbalanced terminal 412 of the second balun 303 in a state in which plasmais generated in the internal space of the vacuum container 110 bysupplying a high frequency from the second high-frequency power supply301. Let X2 be the reactance component (inductance component) of theimpedance of the first coil 221 of the second balun 303. In thisdefinition, satisfying 1.5≤X2/Rp2≤5000 is advantageous in stabilizingthe potential of the plasma formed in the internal space of the vacuumcontainer 110. Note that satisfying the condition of 1.5≤X/Rp2≤5000 isnot essential to the eighth embodiment and is an advantageous condition.In the eighth embodiment, even if the condition of 1.5≤X/Rp2≤5000 is notsatisfied, it is possible to obtain the effect of making the potential(plasma potential) of the plasma formed in the internal space (the spacebetween the first electrode 106 and the second electrode 111) of thevacuum container 110 insensitive to the state of the inner surface ofthe vacuum container 110 by providing the ground electrode 400 in thevacuum container 110.

The plasma processing apparatus 1 according to the eighth embodiment canfurther include at least one of a mechanism for vertically moving thethird electrode 141 and a mechanism for rotating the third electrode141. In the example shown in FIG. 17 , the plasma processing apparatus 1includes a driving mechanism 114 having both the mechanism forvertically moving the third electrode 141 and the mechanism for rotatingthe third electrode 141. Furthermore, in the example shown in FIG. 17 ,the plasma processing apparatus 1 includes a mechanism 314 forvertically moving the fourth electrode 145. Bellows forming vacuumpartitions can be provided between the vacuum container 110 and thedriving mechanisms 114 and 314.

A comparative example will be described below with reference to FIGS. 18to 21 . As shown in FIG. 18 , a plasma processing apparatus 1′ accordingto the comparative example has a structure obtained by eliminating thebaluns 103 and 303 and the ground electrode 400 from the plasmaprocessing apparatus 1 according to the eighth embodiment. Note that inFIG. 18 , a third electrode 141 and a fourth electrode 145 are notillustrated. FIGS. 19 to 21 each show a simulation result of a plasmapotential, the potential (cathode 1 potential) of a first electrode 105a, and the potential (cathode 2 potential) of a second electrode 105 b.In this simulation, high-frequency power supplies 101 a and 101 b areset to generate a voltage of 100 sin(ωt) [V]. The radius of each of thefirst electrode 105 a and the second electrode 105 b is set to 10 cm. Inaddition, in FIGS. 19 to 21 , [cathode 1 area:ground area:cathode 2area] represents [the area of the first electrode 105 a]:[the area of aportion of the vacuum container 110, which functions as an anode]:[thearea of the second electrode 105 b].

FIG. 19 shows a simulation result when cathode 1 area:groundarea:cathode 2 area is 1:0.5:1. FIG. 20 shows a simulation result whencathode 1 area:ground area:cathode 2 area is 1:1:1. FIG. 21 shows asimulation result when cathode 1 area:ground area:cathode 2 area is1:3:1. When forming a film on a substrate 112 by sputtering, a film canalso be formed on the inner surface of a vacuum container 110. This canchange the state of the inner surface of the vacuum container 110, forexample, the area (ground area) of the portion of the vacuum container110, which functions as an anode. With reference to the results shown inFIGS. 19 to 21 , the plasma potential can change due to a change inground area. This indicates that if film formation is continued for aplurality of substrates, the plasma potential can change to change thecharacteristic for forming a film. Furthermore, the results shown inFIGS. 19 to 21 , a larger area (ground area) of the portion of thevacuum container 110, which functions as an anode is more effective insuppressing a change in plasma potential.

On the other hand, according to the eighth embodiment, it is possible tostabilize the potential of the plasma formed in the internal space ofthe vacuum container 110 by providing the balun 103 and the groundelectrode 400 and satisfying the condition of 1.5≤X/Rp1≤5000, asdescribed above. Alternatively, it is possible to stabilize thepotential of the plasma formed in the internal space of the vacuumcontainer 110 by providing the baluns 103 and 303 and the groundelectrode 400 and satisfying the conditions of 1.5≤X/Rp1≤5000 and1.5≤X/Rp2≤5000.

Furthermore, according to the eighth embodiment, even if the conditionof 1.5≤X/Rp1≤5000 is not satisfied, it is possible to stabilize thepotential of the plasma formed in the internal space of the vacuumcontainer 110 by providing the balun 103 and the ground electrode 400.Alternatively, according to the eighth embodiment, even if theconditions of 1.5≤X/Rp1≤5000 and 1.5≤X/Rp2≤5000 are not satisfied, it ispossible to stabilize the potential of the plasma formed in the internalspace of the vacuum container 110 by providing the balun 103 and theground electrode 400.

FIG. 22 schematically shows the arrangement of a plasma processingapparatus 1 according to the ninth embodiment of the present invention.The plasma processing apparatus 1 according to the ninth embodiment canoperate as an etching apparatus that etches substrates 112 a and 112 b.The plasma processing apparatus 1 according to the ninth embodiment isdifferent from that according to the eighth embodiment in that a firstelectrode 105 a and a second electrode 105 b hold the first substrate112 a and the second substrate 112 b to be etched, respectively, and athird electrode 141 holds no substrate. In terms of the remainingpoints, the plasma processing apparatus 1 according to the ninthembodiment can have an arrangement similar to that of the plasmaprocessing apparatus 1 according to the eighth embodiment.

The present invention is not limited to the above-described embodiments,and various changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention, the following claims are made.

REFERENCE SIGNS LIST

1: plasma processing apparatus, 10: main body, 101: high-frequency powersupply, 102: impedance matching circuit, 103: balun, 104: blockingcapacitor, 106: first electrode, 107, 108: insulator, 109: target, 110:vacuum container, 111: second electrode, 112: substrate, 201: firstunbalanced terminal, 202: second unbalanced terminal, 211: firstbalanced terminal, 212: second balanced terminal, 251: first terminal,252: second terminal, 221: first coil, 222: second coil, 223: thirdcoil, 224: fourth coil, 400: ground electrode, PLT: plate portion, PL:plane, HS1: first holding surface, HS2: second holding surface

The invention claimed is:
 1. A plasma processing apparatus comprising: abalun including a first unbalanced terminal, a second unbalancedterminal, a first balanced terminal, and a second balanced terminal; agrounded vacuum container; a first electrode electrically connected tothe first balanced terminal; a second electrode electrically connectedto the second balanced terminal; and a ground electrode arranged in thevacuum container and grounded, wherein the ground electrode includes aplurality of plate portions arranged to be parallel to each other. 2.The plasma processing apparatus according to claim 1, wherein theplurality of plate portions are arranged so that the ground electrodehas a comb-tooth shape in a section.
 3. The plasma processing apparatusaccording to claim 1, wherein the first electrode includes a firstholding surface configured to hold a first member, the second electrodeincludes a second holding surface configured to hold a second member,and the first holding surface and the second holding surface belong toone plane.
 4. The plasma processing apparatus according to claim 3,wherein the ground electrode is arranged to intersect the one plane. 5.The plasma processing apparatus according to claim 4, wherein the groundelectrode includes a portion arranged between the first member and thesecond member.
 6. The plasma processing apparatus according to claim 3,wherein the first holding surface opposes an internal space of thevacuum container via the first member, and the second holding surfaceopposes the internal space of the vacuum container via the secondmember.
 7. The plasma processing apparatus according to claim 3, furthercomprising: a second balun including a third unbalanced terminal, afourth unbalanced terminal, a third balanced terminal, and a fourthbalanced terminal; a third electrode electrically connected to the thirdbalanced terminal; and a fourth electrode electrically connected to thefourth balanced terminal, wherein the fourth electrode is arrangedaround the third electrode, and the third electrode and the fourthelectrode are arranged to oppose the one plane.
 8. The plasma processingapparatus according to claim 7, wherein when Rp represents a resistancecomponent between the first balanced terminal and the second balancedterminal when viewing a side of the first electrode and the secondelectrode from a side of the first balanced terminal and the secondbalanced terminal, and X represents an inductance between the firstunbalanced terminal and the first balanced terminal, 1.5≤X/Rp ≤5000 issatisfied, and when Rp′ represents a resistance component between thethird balanced terminal and the fourth balanced terminal when viewing aside of the third electrode and the fourth electrode from a side of thethird balanced terminal and the fourth balanced terminal, and X′represents an inductance between the third unbalanced terminal and thethird balanced terminal, 1.5≤X′/Rp′≤5000 is satisfied.
 9. The plasmaprocessing apparatus according to claim 1, wherein the first balancedterminal and the first electrode are electrically connected via ablocking capacitor.
 10. The plasma processing apparatus according toclaim 1, wherein the second balanced terminal and the second electrodeare electrically connected via a blocking capacitor.
 11. The plasmaprocessing apparatus according to claim 1 wherein the first balancedterminal and the first electrode are electrically connected via ablocking capacitor, and the second balanced terminal and the secondelectrode are electrically connected via a blocking capacitor.
 12. Theplasma processing apparatus according to claim 1, wherein the firstelectrode and the second electrode are supported by the vacuum containervia insulators.
 13. The plasma processing apparatus according to claim1, wherein the balun includes a first coil configured to connect thefirst unbalanced terminal and the first balanced terminal, and a secondcoil configured to connect the second unbalanced terminal and the secondbalanced terminal.
 14. The plasma processing apparatus according toclaim 1, wherein the first electrode holds a first target, the secondelectrode holds a second target, the first electrode opposes a space ona side of a substrate as a processing target via the first target, andthe second electrode opposes the space via the second target.
 15. Theplasma processing apparatus according to claim 1, wherein the firstelectrode holds a first substrate, the second electrode holds a secondsubstrate, and the plasma processing apparatus is configured as anetching apparatus configured to etch the first substrate and the secondsubstrate.
 16. The plasma processing apparatus according to claim 1further comprising: a high-frequency power supply; and an impedancematching circuit arranged between the high-frequency power supply andthe balun.
 17. The plasma processing apparatus according to claim 1,wherein when Rp represents a resistance component between the firstbalanced terminal and the second balanced terminal when viewing a sideof the first electrode and the second electrode from a side of the firstbalanced terminal and the second balanced terminal, and X represents aninductance between the first unbalanced terminal and the first balancedterminal, 1.5≤X/Rp≤5000 is satisfied.
 18. A plasma processing apparatuscomprising: a balun including a first unbalanced terminal, a secondunbalanced terminal, a first balanced terminal, and a second balancedterminal; a grounded vacuum container; a first electrode electricallyconnected to the first balanced terminal; a second electrodeelectrically connected to the second balanced terminal; and a groundelectrode arranged in the vacuum container and grounded, wherein theground electrode has a comb-tooth shape in a section.
 19. A plasmaprocessing apparatus comprising: a balun including a first unbalancedterminal, a second unbalanced terminal, a first balanced terminal, and asecond balanced terminal; a grounded vacuum container formed by aconductor; a first electrode electrically connected to the firstbalanced terminal; a second electrode electrically connected to thesecond balanced terminal; and a ground electrode arranged in the vacuumcontainer and grounded; wherein the balun includes a first coilconfigured to connect the first unbalanced terminal and the firstbalanced terminal, and a second coil configured to connect the secondunbalanced terminal and the second balanced terminal, a third coil and afourth coil both of which are connected between the first balancedterminal and the second balanced terminal, and the third coil and thefourth coil are configured to set, as a midpoint between a voltage ofthe first balanced terminal and a voltage of the second balancedterminal, a voltage of a connection node of the third coil and thefourth coil.